The present invention relates to an air conditioner system and method for electric vehicles.
Heat pump type air conditioner systems employing electrically-driven compressors are used widely as air conditioners mounted on electric vehicles from the standpoint of ensuring a self heat generating source, reducing air pollution and saving electric power energy. In those heat pump type air conditioner systems, however, the exterior heat exchanger is used as an evaporator at the time of heating operation to exchange heat between low temperature, low pressure refrigerant and exterior air. Thus, frosting occurs on the surface of the heat exchanger at the time of heating operation. The frosting lessens the operation performance of exchanging heat with the exterior air and hence the heating operation performance.
U.S. Pat. No. 5,555,737 (JP-A-7-212902) proposes to defrost the heat exchanger in the course of battery charging by using excess electric power generated immediately before completing the battery charging. The heat exchanger will not be defrosted sufficiently when the battery charging is stopped midway of the battery charging, that is, before the battery charging is completed. As a result, a sufficient heating performance for a quick heating (warm-up) cannot be provided as the heating operation starts with frost still remaining on the heat exchanger.